Figure 1

An illustration of possible structural configurations of the model (2). (a) A corner-sharing CuO${}_2$ spin-1/2 Heisenberg chain as contained in Sr${}_2$CuO${}_3$ with the yellow plane being a mirror symmetry plane with two high symmetry lines (green online). (b) The side view of a spin-1/2 Heisenberg chain coupled by a triangular CoO${}_2$ cluster allocated to one of the high symmetry lines. (c) Three chains coupled by a triangular CoO${}_2$ cluster viewed along the chain direction. (d) A six-chain system coupled by a six-spin cluster. ${\mathcal{J}}_p$ is the antiferromagnetic exchange coupling between the $p$th chain and the cluster. The ferromagnetic interaction within the cluster might be realized by the ${90}^{\circ }$ Co-O-Co exchange pathways (Refs. 18 and 19).Reuse & Permissions